Seeded Lawn - Weeds, Weed & Feed

I spread grass seed in my backyard about a month and a 1/2 ago and the grass is growing nicely except in patches! So I reseeded it last week concentrating on the bare patches. My problem is weeds are also growing and is beginning to take over the whole area! I was wondering if anyone can tell me if using things like lawn feed & weed would kill the freshly sprouting grass or is it safe for the newly sprouted grass/seedlings! Any help or advice would be greatly appreciated.